How to Conditionally Format a String in .Net?

Question

I would like to do some condition formatting of strings. I know that you can do some conditional formatting of integers and floats as follows:

Int32 i = 0;
i.ToString("$#,##0.00;($#,##0.00);Zero");

The above code would result in one of three formats if the variable is positive, negative, or zero.

I would like to know if there is any way to use sections on string arguments. For a concrete, but contrived example, I would be looking to replace the "if" check in the following code:

string MyFormatString(List<String> items, List<String> values)
{
    string itemList = String.Join(", " items.ToArray());
    string valueList = String.Join(", " values.ToArray());

    string formatString;

    if (items.Count > 0)
    //this could easily be: 
    //if (!String.IsNullOrEmpty(itemList))
    {
        formatString = "Items: {0}; Values: {1}";
    }
    else
    {
        formatString = "Values: {1}";
    }

    return String.Format(formatString, itemList, valueList);
}

Answer 1

This is probably not what you're looking for, but how about...

formatString = (items.Count > 0) ? "Items: {0}; Values: {1}" : "Values: {1}";

Answer 2

Not within String.Format(), but you could use C#'s inline operators, such as:

return items.Count > 0 
       ? String.Format("Items: {0}; Values: {1}", itemList, valueList)
       : String.Format("Values: {0}", valueList);

This would help tidy-up the code.

Answer 3

Well, you can simplify it a bit with the conditional operator:

string formatString = items.Count > 0 ? "Items: {0}; Values: {1}" : "Values: {1}";
return string.Format(formatString, itemList, valueList);

Or even include it in the same statement:

return string.Format(items.Count > 0 ? "Items: {0}; Values: {1}" : "Values: {1}",
                     itemList, valueList);

Is that what you're after? I don't think you can have a single format string which sometimes includes bits and sometimes it doesn't.

Answer 4

I hoped this could do it:

return String.Format(items.ToString(itemList + " ;;") + "Values: {0}", valueList);

Unfortunately, it seems that the .ToString() method doesn't like the blank negative and zero options or not having a # or 0 anywhere. I'll leave it up here in case it points someone else to a better answer.

Answer 5

string.Format(  (items.Count > 0 ? "Items: {0}; " : "") + "Values {1}"
              , itemList
              , valueList);